Add type annotations to caster.js.

Add type annotations to caster.js.

BUG=444485
TEST=GYP_GENERATORS=ninja tools/gyp/gyp --depth . ui/file_manager/video_player/js/compiled_resources.gyp && ninja -C out/Default | grep "caster.js"

Committed: https://crrev.com/ac340a287a4efa9febff64a3c62cf1e1f1d96ca4
Cr-Commit-Position: refs/heads/master@{#309623}

[yawano, 2014-12-24 06:34:41]

yawano@chromium.org changed reviewers:
+ yoshiki@chromium.org

[yawano, 2014-12-24 06:34:41]

PTAL. Thank you!

[yoshiki, 2014-12-24 07:47:47]

lgtm

[yawano, 2014-12-24 07:48:27]

On 2014/12/24 07:47:47, yoshiki wrote:
> lgtm

Thank you!

[yawano, 2014-12-24 07:48:31]

The CQ bit was checked by yawano@chromium.org

[commit-bot: I haz the power, 2014-12-24 07:49:30]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/823583005/1

[commit-bot: I haz the power, 2014-12-24 08:34:30]

Committed patchset #1 (id:1)

[commit-bot: I haz the power, 2014-12-24 08:35:19]

Patchset 1 (id:??) landed as
https://crrev.com/ac340a287a4efa9febff64a3c62cf1e1f1d96ca4
Cr-Commit-Position: refs/heads/master@{#309623}